/* ----------------------------------------------------------------------
* Copyright (C) 2010 ARM Limited. All rights reserved.
*
* $Date:        15. February 2012
* $Revision: 	V1.1.0
*
* Project: 	    CMSIS DSP Library
* Title:		arm_power_q15.c
*
* Description:	Sum of the squares of the elements of a Q15 vector.
*
* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
*
* Version 1.1.0 2012/02/15
*    Updated with more optimizations, bug fixes and minor API changes.
*
* Version 1.0.10 2011/7/15
*    Big Endian support added and Merged M0 and M3/M4 Source code.
*
* Version 1.0.3 2010/11/29
*    Re-organized the CMSIS folders and updated documentation.
*
* Version 1.0.2 2010/11/11
*    Documentation updated.
*
* Version 1.0.1 2010/10/05
*    Production release and review comments incorporated.
*
* Version 1.0.0 2010/09/20
*    Production release and review comments incorporated.
* -------------------------------------------------------------------- */

#include "arm_math.h"

/**
 * @ingroup groupStats
 */

/**
 * @addtogroup power
 * @{
 */

/**
 * @brief Sum of the squares of the elements of a Q15 vector.
 * @param[in]       *pSrc points to the input vector
 * @param[in]       blockSize length of the input vector
 * @param[out]      *pResult sum of the squares value returned here
 * @return none.
 *
 * @details
 * <b>Scaling and Overflow Behavior:</b>
 *
 * \par
 * The function is implemented using a 64-bit internal accumulator.
 * The input is represented in 1.15 format.
 * Intermediate multiplication yields a 2.30 format, and this
 * result is added without saturation to a 64-bit accumulator in 34.30 format.
 * With 33 guard bits in the accumulator, there is no risk of overflow, and the
 * full precision of the intermediate multiplication is preserved.
 * Finally, the return result is in 34.30 format.
 *
 */

void arm_power_q15(
    q15_t* pSrc,
    uint32_t blockSize,
    q63_t* pResult)
{
	q63_t sum = 0;                                 /* Temporary result storage */

#ifndef ARM_MATH_CM0

	/* Run the below code for Cortex-M4 and Cortex-M3 */

	q31_t in32;                                    /* Temporary variable to store input value */
	q15_t in16;                                    /* Temporary variable to store input value */
	uint32_t blkCnt;                               /* loop counter */


	/* loop Unrolling */
	blkCnt = blockSize >> 2u;

	/* First part of the processing with loop unrolling.  Compute 4 outputs at a time.
	 ** a second loop below computes the remaining 1 to 3 samples. */
	while(blkCnt > 0u) {
		/* C = A[0] * A[0] + A[1] * A[1] + A[2] * A[2] + ... + A[blockSize-1] * A[blockSize-1] */
		/* Compute Power and then store the result in a temporary variable, sum. */
		in32 = *__SIMD32(pSrc)++;
		sum = __SMLALD(in32, in32, sum);
		in32 = *__SIMD32(pSrc)++;
		sum = __SMLALD(in32, in32, sum);

		/* Decrement the loop counter */
		blkCnt--;
	}

	/* If the blockSize is not a multiple of 4, compute any remaining output samples here.
	 ** No loop unrolling is used. */
	blkCnt = blockSize % 0x4u;

	while(blkCnt > 0u) {
		/* C = A[0] * A[0] + A[1] * A[1] + A[2] * A[2] + ... + A[blockSize-1] * A[blockSize-1] */
		/* Compute Power and then store the result in a temporary variable, sum. */
		in16 = *pSrc++;
		sum = __SMLALD(in16, in16, sum);

		/* Decrement the loop counter */
		blkCnt--;
	}

#else

	/* Run the below code for Cortex-M0 */

	q15_t in;                                      /* Temporary variable to store input value */
	uint32_t blkCnt;                               /* loop counter */


	/* Loop over blockSize number of values */
	blkCnt = blockSize;

	while(blkCnt > 0u) {
		/* C = A[0] * A[0] + A[1] * A[1] + A[2] * A[2] + ... + A[blockSize-1] * A[blockSize-1] */
		/* Compute Power and then store the result in a temporary variable, sum. */
		in = *pSrc++;
		sum += ((q31_t) in * in);

		/* Decrement the loop counter */
		blkCnt--;
	}

#endif /* #ifndef ARM_MATH_CM0 */

	/* Store the results in 34.30 format  */
	*pResult = sum;
}

/**
 * @} end of power group
 */
